docs: def _standard_frame_length(header):
      """Calculates the length of a standard ciphertext frame, given a complete header.
  
      :param header: Complete message header object
      :type header: aws_encryption_sdk.structures.MessageHeader
      :rtype: int
      """
      frame_length = 4  # Sequence Number
      frame_length += header.algorithm.iv_len  # IV
      frame_length += header.frame_length  # Encrypted Content
      frame_length += header.algorithm.auth_len  # Authentication Tag
      return frame_length